Press with rapid-closing upwardacting ram



Dec. 17, 1940. w ERNST E L 2,224,956

PRESS WITH RAPID-CLOSING URWARD-ACTING RAM Filed May 23,-1958 e Sheds-Sheet 2 2 26 Inventors V T 1;; I

' 21 WALTER Exp/v57- Attorneys Dec. 17, 1940. w ERNST ETAL 2,224,956

7 PRESS WITH RAPID-CLOSING UPWARD--ACTING'RAM Filed May 25, 1938 S SheetS-Sheet '3 IN VENTORS ATTORNEYS 6 Sheets-Sheet 5 Dec. 17, 1940.

T 67 5 A 5 y a? H x N Z M 9 VF JT Z 4 z 561. 4 .z 105 A Z 0. ill! a k 5 m 7 E 4): vM .1 1m l Dec. 17, 1940. w, ERNST ETAL 2.224356 PRESS WITH RAPID-CLOSING .UPWARD-ACTiNG RAM Filed May 23, 19:58 6 Sheets-Sheet e 1 Attorneys Patented Dec. 17, 1940 v 2,224,956 mass wrrn mm-ctosmc urw PATENT OFFICE ACTING RAM Walter Ernst, Mount Gilead, and Leslie S.

Hubbert, Edison, Ohio, assignors to The Hydraulic Development Corp, 1110., Wilmington, Del., a corporation of Delaware Application May 23, 1938, Serial No, 209,484

2 Claims. (Cl. 60-51) This invention relates to presses, and in particular, to upwardly acting hydraulic presses.

, One object of this invention is to provide a hydraulic press with an upwardly acting plunger,

together with means for insuring the rapid closing of the press.

Another object of this invention isto provide a hydraulic press with an upwardly acting main plunger having mechanism actuated by a substantially constant'pressure source for rapidly advancing the plunger to the pressing position,

this pressure source being independent of the pressure source which operates the press.

Another object is to provide a hydraulic press with an upwardly acting main plunger having auxiliary plungers, which are actuated to rapidly advance the main plunger to the working position by means of pressure from an independent pressure source apart from the pressure source which operates the press.

Another object is to provide a hydraulic press with an upwardly acting main plunger of the type described above, wherein the independent pressure source for rapidly advancing the plunger .to the working position consists of a gas-loaded or fluid-loaded accumulator.

Another object is to provide a hydraulic press with an upwardly acting main plunger, together with means for rapidly advancing the main plunger to the working position, and means, such as a surge valve, for replenishing the liquid required by the main cylinder as the plunger advances, preferably from an auxiliary tank at the base of thepress, and supplied with fluid from a main surge tank at the-top of the press. v

Another object is to .provide a hydraulic press with an upwardly acting main plunger of the type described in thepreceding object, wherein the surge valve is double acting with hydraulic connections for forcibly opening it in response to the commencement of the return stroke .of the press, so asto permit the fluid from the main cylinder to pass immediately into the auxiliary tankfwhence it may flow backto the main surge tank.

Another object is to provide an accumulatoractuated system for rapidly advancing an up wardly acting hydraulic plunger to the working position, together with means for preventing leakage of the gas for bringing about the rapid advance of the main plunger or platen, such as for example, by a gas-loaded accumulator which actuates an intermediate liquid for transmitting its force to the auxiliary plungers, which advance the main plunger or main platem- I r advancing a main plunger or platen to the working position,.employing the principles of the press shoWninFigureslandZ. a

Figure 4 is a fragmentary front elevation,-partly in section, of a press employing a liquid to transmit the force from the accumulator to the auxiliary plungers for rapidly advancing the platen so as to prevent leakage of the gas.

Figure 5 is a fragmentary vertical section through a modification of Figure 4, employing a weight-loaded accumulator instead of a gasloaded accumulator."

Figure 6 is a diagrammatic front elevation, partly in section, showing another modified form of press embodying the principles of the invention. v V

Figure 7 is a front elevation, partly in 'section; of a commercial form of press slightly modified from thatishown in Figures 1 and 2, and disclos- 3 ing the pump and its control system more clearly.

General arrangement The auxiliary plungers are actuated from a substantially constant pressure source, which is independent of the pressure source for operating the press. Preferably, this pressure source-consists of a gas-loaded or weight-loaded accumulator adapted to exert a substantially constant pressure load standing against the platen substantially all of the time. The gas pressure for actuating the auxiliary plungers is either applied directly to a pneumatic plunger connected to the auxiliary plungers, as in Figures 1, 2, 3 and 6, or else it exerts its force against an intermediate column of liquid which transmits this force to the auxiliary plungers. Figure 5 substitutes a weight-loaded accumulator for the gas-loaded accumulator in the circuit of Figure 4. The press shown in Figures 1, 2 and 3 employs a pneumatically actuated piston head of larger area than the hydraulically actuated piston heads of the auxiliary plungers, so that a lower gas pressure can be employed to counterbalance a considerably higher hydraulic pressure.

In these presses the main plunger is retracted by hydraulic pressure supplied to the auxiliary plungersfrom a pump. These auxiliary plungers are forced downwardly against the resistance of the force coming from the accumulator so that this force is accumulated in the form of potential energy, which is ready at any moment to be utilized for advancing the main plunger. .In this manner no energy is lost in the means for rapidly advancing the main plunger to the working position, aside from the slight losses due to friction, etc. because the moving parts are, in effect, floated by the pressure of confined air or other gas. When the platen is retracted, pistons, actuated .by the return of the platen, restore the com-.

pression to the air or actuate a weight-loaded accumulator so that no energy is Wasted. In this manner a rapid response and high speed of action-are obtained because the compressed gas is quick to act. Furthermore, a small pump sufflces to supply pressure fluid to the main plunger because the pump is not depended upon for rapid advancing of the main plunger to the working position.

Hitherto, in upwardly acting hydraulic presses, it has been diflicult to cause the platen to rapidly approach the working position. Ordinarily, a considerable portion of the movement of the main plunger and platen of a hydraulic press is expended merely in bringing the platen into working position, where it begins to exert pressure upon the workpiece. During this approach motion little or no force is required to move the plunger other than that which is necessary to lift the moving parts. As no useful work is performed during this approach period, it is desirable to keep the time of this movement as short as possible. Furthermore, for many kinds of Work heavypressing pressure is required only during a very small portion of the stroke of the main lunger, sometimes, indeed, for only a fraction of 11 inch of motion.

Due to this small motion required, a comparatively small hydraulic pump would sufiice to supply pressure fluid in such cases, because the movement under high pressure is very small, and ience, a relatively smallamount of fluid is required to build up a high pressure in the press cylinder and perform the desired work. A small pump, however, if depended upon for raising the "min plunger and platen of a large press to the vorking position would require a long period of time. If auxiliary plungers and auxiliary cylinders are employed, a small pump will give a much more rapid speed of advance than if actingupon the much larger area of the main plunger. In

rder to utilize such auxiliary plungers, however, additional valve equipment must be supplied for changing the flow of pressure fluid from the main cylinder to the auxiliary cylinders, and vice versa. Furthermore, the energy expended for lifting the heavy moving parts by means of these auxiliary plungers is entirely wasted under these circumstances.

In our invention, as stated above, this energy is not wasted because it is stored-up in an accumulating device when the main plunger is retracted. No superfluous valve equipment is required because an entirely independent source of energy is relied upon for advancing the platen to the working position. The pump is depended upon merely for supplying pressure fluid to the main plunger during the short pressing stroke after the platen has advanced to the working position, and also for retracting the main plunger by means of auxiliary plungers.

Press construction Referring to the drawings in detail, Figures 1 I and 2 show a commercial embodiment of the invention, consisting of an upwardly acting hydraulic press. This press includes a bed l0 and a head ll, interconnected by strain rods l2 and resting upon a foundation l3. The strain rods l2 have nuts [4 at their opposite ends for holding this assembly together. Formed integral with the bed In are main cylinders l5 and auxiliary cylinders 16. For supplying fluid to these cylinders the press head ll supports a surge tank I1, connected by a conduit l8 with a valve l9 to the auxiliary .tank 20. The valve I9 is supplied merely to cut off the surge tank I! to prevent loss of fluid in the event that the piping is disconnected at lower levels so that it will not be necessary to drain the main tank.

Running from the auxiliary tank 20 to the main cylinders I5 is a conduit 2| communicating with a passageway 22 in the bed I0 of the press. This passageway 22 is T-shaped and communicates at its upper ends with the two main cylin- .prefllling the main cylinders l5 during the advancing stroke, and also of permitting the direct emptying thereof during the retraction stroke. For this purpose the surge valve 24 is provided with a valve casing 25 having a spring 26, urging a valve member 21 upwardly into position for closing the valve port 28. The spring 26 exerts a gentle pressure so that the valve member 21 is easily opened whenever suction is created in the conduit 2| in response to the suction created in the main cylinders I5 during the advancing stroke of the press. Under these circumstances, fluid may flow directly from the auxiliary tank 20, through the valve port 28, into the conduit 2|, and thence through the passageway 22, into the main cylinders, displacing the valve member 21 for forcibly opening the valve during the retraction stroke of the press. For this purpose there is mounted above the valve casing 25 a hydraulic cylinder 3| containing a cylinder. bore 32,.within which a piston head 33 is reciprocable. The piston head 33 is mounted upon apiston rod 34, the lower end of which emerges from the cylinder 3| and engages the top of the valve member 21. A coil spring 35 within the cylinder bore 32 normally urgesthe piston head 33 upwardly to permit the closing of the valve member 21 by the coil spring 26. Connected to a port 36 in the top of the cylinder bore 32 is a conduit 31 leading to the retraction line'38, which runs to the ports 39 in the upper ends of the auxiliary cylinders IS. The retraction line 38 is connected at its opposite end to the junction 40 upon the conduit connection 4|, having a junction 42. Running from the latter is the conduit 43 (Figure 2) leading to the conduit 2|. The conduit connection 4| is secured to the side of a reversible variable delivery pump 44 having a hand wheel 45 for controlling its action, as hereinafter disclosed more in detail. The details of the pump 44 form no part of the present invention, and any suitable type of pump may be employed. The conduit 43 supplies pressure fluid to the main cylinders l to cause the completion of the working stroke after the press has been advanced to'the working position by the devices of th present invention. 1,

Reciprocable in the main cylinders I5 are main plungers 46, connected at their upper ends to a platen 41 arranged to be advanced into engagement with the thrust-portion 48 upon the' press head H. Connected to the platen arms 49, at the ends of the platen 41, are auxiliary plungers 50, consisting of piston rods 5| having piston heads 52 thereon, reciprocable within the auxiliary cylinders 16. The lower ends of the piston heads 52 age, engaged by the upper ends of separate piston ds 53, having on their lower ends piston headsf 54, reciprocablein cylinder bores 55 within the pneumatic cylinders 56. The pneumatic cylinders 56 are secured to .the bed of the press, immediately below the auxiliary cylinders l6. Ports .51 are provided for the escape of air above the piston heads 54. The pneumatic cylinders 56 are closed by cylinder heads 58, having ports 59 therein communicating with the line 60 leading to a pressure source or accumulator 61 (Figures 3, 4 and 5). Around the piston rods 53 are oil seals 62 for preventing the oil within the cylinders Hi from leaking downwardly into the cylinder bores 55. For returning such leakage fluid to the auxiliary tank placement of th stroke of the pneumatic pistons 54, so that the, latter may make their strokes without seriously decreasingthe pressure within the pressure source 61. It will be understood that means (not shown) is provided for adding air or other gas to the pressure source 61 from time to time, as may be required to make up for any leakage which may'occur' past the pistons The pressure source 6| is preferably of ten or more times the combined disof a solenoid 14 pivotally connected to its outer end by means of the connecting rod (Figure 2). ,When the solenoid 14 is energized it pulls the outer end of the yoke-shaped lever" 1| downwardly, and likewise moves the control rod 61 downwardly. To oppose this action the control rod 61 is normally urged upwardly by a spring (not shown). The control rod 61 may likewise be actuated by means of a hand lever 16, piv otally mounted as at 11 (Figure 1) upon the bed 10 of the press, and having an arm 18, the outer end of which is arranged to engage the collar 19 upon the control rod 61. The control rod 61 likewise carries adjustable collars 80 and 8|, arranged to be engaged by the opposite sides of a platen extension 92 as the platen 41 moves up and down. The control rod 61 further carries a cam 83 adapted to engage the switch lever 84 of a limit switch 85, connected in the energization circuit of the solenoid 14.

On the lower end of the control rod 61 are spaced collars 86, arranged to engage the yokeshaped end of a bellcrank 91, pivotally mounted as at 88,- Pivotally connected to the upper end of the bellcrank 81 is a connecting rod 89, the opposite end of which (Figure '1) is pivotally connected to the lower end of a lever 90, pivotally mounted on the floating fulcrum link 9| and pivotally connected at its upper end to the servomotor valve control rod 92. The latter controls the operation of the servomotor valve, generally designated 93, attached to the pump 44. The servomotor valve 93 controls the direction of actuation of the pump servomotor, generally designated 94, for moving the flow-varying member of the pump to and fro in order to vary or reverse the delivery of the pump 44. Also mounted upon the pump 44 is the pump control casing 95, containing a spring arrangement (notshown) for adjusting the pressure at which the pump control becomes operative to shift the flow-control member of the pump to its neutral position and thus cut down the delivery of the pump to zero. Emerging from the pump control casing 951s a shaft 96, carrying the previously-mentioned hand wheel 45. By rotating the hand wheel 45 and the shaft 96, the spring tension within the pump control casing 95 may be varied for varying'the pressure at which the pump 44 is automatically placed in a neutral or zero delivery condition.

Also mounted upon the bed III of the press is the tonnage controller 91, having a hand'wheel 98 for rotating the screw shaft 99 in order to regulate the pressure at-which the press circuit is reversed to confinenee the retraction stroke.

The. ton r3ge \contioller 91 is, in effect, a pressure Switch connected in circuit with the solenoid 15, and arranged to break the energization circuit thereof when the pressure in the main cylinders 15 reaches a predetermined amount. For this purpose the tonnage controller 91 is connected to the passageway 22 leading to the main cylinders 15 by means of the conduit I00. The rotation of the hand wheel 98, therefore, regulates thepressure at which the pressure switch within the tonnage controller 91 becomes operative by pressure reaching it through the conduit I00. The pump 44 is driven by an electric motor IOI.

Operation In the operation of the press shown in Figures 1 and 2, let it be assumed that the various moving parts of the press are in the positions shown in these figures. To start the press the operator either pushes upon the hand lever 16 or closes an electrical switch which energizes the solenoid 14. Either of these operations causes the control rod 61 to be moved downwardly, thereby shifting the servomotor'control rods 89 and 92 to move the shift ring, or other flow-control member of the pump 44, so as to cause the pump to exhaust oil from the connection 40 and the line 38, leading to'the auxiliary cylinders 36 above the auxiliary piston heads 52. The oil thus withdrawn is pumped through the connection 42 and conduit 43, into the conduit 2i at the port I02 (Figure 2).

As fast as the oil is removed from the auxiliary cylinders I6 by means above described, the auxiliary piston heads 52 are moved upwardly by the air pressure beneath the pneumatic piston heads 54. This action causes the piston rods 53 to raise the pistons 52, the piston rods i, the platen arms 49, the platen 41 and the main plungers 46, creating a suction within the main cylinders I5. This suction causes the valve member 21 of the surge valve 24 to move downwardly into its open position, thereby withdrawing oil through the valve ports 30, 28, and 29 from the auxiliary tank 20, so as to fill the main cylinders I5 and relieve this suction. Meanwhile, the auxiliary tank 20 is replenished by oil reaching it through the conduit I8 from the main surge tank I1 upon the head II of the press.

When the platen 41 reaches its working position and engages the workpiece, or otherwise meets such resistance that it can no longer be pushed upwardly by air pressure, the flow of oil from the pump 44, through the line 43, builds up pressure within the conduit 2i, the passageway 22 and the main cylinders I5 so' that the surge valve 24 closes and the main plungers 43 are moved upwardly in response to the pressure from the pump 43.

The press may be arranged for any desired type of reversal, the circuit shown being arranged for pressure reversal; When the pressure in the main cylinders I5 reaches a predetermined value, depending upon the setting of the tonnage controller 91, the switch within the latter opens in response to the pressure reaching it along the line I00, and deenergizes the solenoid 14. With the solenoid 1 3 deenergizecl, the control rod 61 is free to move upwardly, and a spring associated with the servomotor 96 pulls the flow-control member or shift ring of the pump M to its reverse position, thereby creating suction at the connection 42 and pressure at the connection 40. In response to this reversal of the pump 40, oil under pressure is now pumped through the line 38, into the auxiliary cylinders i6 above the piston heads 52, forcing them downwardly against the pneumatic pressure being exerted against the pneumatic piston heads 56 Within the pneumatic cylinders 56.

At the same time oil under pressure passes along the conduit 38, through the conduit 31 to v the cylinder bore 32 within the cylinder 3i of the surge valve 24, forcing the piston rod 34 downwardly and forcibly opening the valve member 21 of the surge valve 24. This action permits the oil to escape from the main cylinders I5, through the passageway 22, conduit 2| and surge valve ports 29, 28 and 30 directly into the auxiliary tank 20. The suction created lnthe line 43 also assists in withdrawing some of this oil from the conduit 2| by way of the port I02 (Figure 2). The gas that is forced out from beneath the pistons 54 in the pneumatic cylinders 56 is returned to the gas pressure source 6|. This gas may be air or any other suitable gas, nitrogen being also found satisfactory for this purpose. If there has been no leakage of gas, therefore, there is now just as much pressure in the gas tank or gas source 6| as there was originally therein. It will be observed, therefore, that the energy required to lift the weight of the platen 41, main plungers 46 and the other movingparts, is restored upon their down strokes.

In series with the switch within the tonnage controller 91 is the normally open limit switch 85, this switch being held closed by the cam 33.

If, however, the operator carelessly operates the press without a workpiece or dies in the press, the platen, through the extension 82, will strike th collar SI and lift the control rod 61 so that the-cam 83 moves off of the switch lever 84 and permits the limit switch 85 to open, thereby deenergizing the solenoid 14 and reversing the press. The same arrangement may likewise be used for position reversal of the platen at a predetermined position, if it is not desired to employ pressure reversal.

Modified press arrangement employing open circuit control The modified circuit shown in Figure 3 is a Simplified arrangement, utilizing the same principles already described in connection with Figures 1 and 2. Instead of the closed circuit of Figures 1 and 2 and a reversible variable delivery pump for operating the circuit, the construction of Figure 8 employs an open .ircuit with a pump I05, arranged to deliver pressure fluid to a four-way valve' I06 by means of the pressure line I01, and to withdraw fluid from the surge tank I1 by means of the suction line I08. It will, of course, be understood that the pump I05 may withdraw pressure fluid from an auxiliary tank, such as the tank shown in Figure 1, this having been omitted from Figure 3 to simplify the showing.

From th four-way valve I06 the discharge line I09 likewise leads back to the surge tank I1, or other receptacle. The four-way valve I06 is arranged in one position to connect the press retraction line 38 to the pump pressure line I01, while connecting the press advancing line 43 to the discharge line I09; and in another position to connect the press advancing line 43 to the pump pressure line I01, while connecting the press retraction line 38 to the discharge line I09. The operation of the circuit of Figure 3 is therefore similar to that of Figure 1, except that the reversal of the circuit is brought about by reversing the position of the four-way valve I 06 rather than by reversing the pump itself. Th four-way valve I06 is operatedeither manually or by a solenoid, as by mechanism similar to the control valve 61 shown in Figures 1 and 2. In place of the surge valve 24 an ordinary check valve 24 is It will be understood that a gas storage tank is preferably interposed in the line 60, the line 60' from the gas cylinder 6I being employed for replenishing the gas in this tank, which has been omitted for simplicity of showing. A v'alve IIO between the line 60 and the line 60'' regulates the admission or replenishment of gas.

In the operation of the circuit shown in Figure 3, to start the press upon a working stroke the valve I06 is shifted to connect the pump pressure line I01 with the line 43 and to connect the retraction line 36 with the discharge line I09. The fluid thus released from the auxiliary cylinders I6 passes into the surge tank I1 by way of the line 38, the valve I06 and the line I08, under the urge of the auxiliary piston heads 52, which are being moved upwardly by the pneumatic piston heads 54 in the pneumatic cylinders 56. In Figure 3, for simplification, the piston rod 53 is shown integral with thepiston rod 5|. As the moving parts rise, under the influence of the compressed gas within the pneumatic cylinder bores 55, the suction thereby created in the main cylinder I5 opens the valve member 21 of the check valve 24 and permits fluid to be drawn into the main cylinders I5 from the surge tank I1 by way of the conduits I8 and 2I and the check valve 24 When the platen 41 encounters the workpiece, or other resistance, the pressure built up in the conduit 2I.from the fluid delivered thereto by the pump I05, through the lines I01 and 43 and the four-way valve I06, causes the check valve member 21 to seat and close. Subsequently the pump I05, therefore, delivers pressure fluid to force the main plunger 46 upwardly to complete the working stroke.

To reverse the press, the operator shifts the control valve I06 and causes pressure fluid to be delivered from the pressure line I01 of the pump I05 to the retraction line 38, whence it flows into the auxiliary cylinders I6 above the piston heads 52, forcing the latter downwardly. This action compresses the air in the pneumatic cylinders 55 by forcing'their pistons 54 downwardly, thereby storing up potential energy which becomes available upon the next advancing stroke of the press for raising the moving parts into the working position. While this is going on, the fluid within the main cylinder I5 is being discharged through the lines 43 and I09 and the four-way valve I06. It will be understood, however, that a double-acting check valve, similar to the check valve 24 in Figure 2, may be used in place of the simple check valve 24*, so that it will be forcibly opened upon the retraction stroke, and permit fluid to pass directly from the main cylinder I5, through the conduits 2| and 16, into the surge tank I1. Any leakage of gas past the pistons 54 will escape through the conduits 54, into the surge tank I1, and thence into the atmosphere. I The spaces above the pneumatic piston heads 54 serve as slippage reservoirs, with the outlets 63 so arranged that a small amount of oil leaking past the piston heads 52 will always remain above the piston heads 54 for lubrication purposes. Any excess leakage of oil, however, returns to the tank I1 by way of the conduits 64, when the pistons54 are in their uppermost positions.

Modified construction for'reducing gas leakage In the modification shown in Figure 4, means is'provided for preventing the leakage and consefqueritloss of. gas past the piston heads 54. This directly, In Figure 4 the auxiliary cylinders I6 are closed at their lower ends by cylinder heads I I I, having ports II 2 therein communicating with a conduit II3, leading to a hydropneumatic accumulator,- generally designated H4. The hydro- "a port I2I, to which the conduit II3is attached.

The cylinder bore I I6 is provided with a port I22, to which a conduit I23 leads from a source of gas.

In the operation of the circuit shown in Figure 4, asmall quantity of oil is placed on top of the piston head IIB for lubrication. purposes, and the bore. II1, the conduit H3 and the chambers I24 beneath the piston heads 52 are filled with oil. The compressed gas ,within the upper cylinder bore II6, acting against the piston head II8, tends to force the oil out of the lower cylinder bore I I1, through the conduit I I3, into the chambers I24 whenever the oil is released from the auxiliary cylinders I above the auxiliary piston heads 52. When the piston heads 52 are forced downwardly in retracting the platen 41, however, the oil is forced back into the lower cylinder bore I I1, causing the piston head II8 to rise and compress the gas in the upper cylinder bore II6, thereby storing up potential energy for the next rapid advance stroke of the main plunger 46, Gas leakage cannot occur in the circuit of Figure 4 unless pressure completely disappears in the lower cylinder bore II1, a situation which is unlikely to occur with a proper design of construction.

The modification shown in Figure 5 is similar to that shown in Figure 4, except that a weightloaded accumulator, generally designated I25, replaces the gas-loaded accumulator H4. The weight-loaded accumulator 'of Figure 5 consists of a-cylinder I26, mounted upon a base I21 in which there is a port I28 connecting the line II3 with the cylinder bore I29. Reciprocable in the cylinder bore I29 is a plunger I39, upon the upper end of which is mounted a head I3I having tie rods I32 depending downwardly therefrom to support an annular platform I33, upon which an annular counterweight I34 rests. A gland I35 prevents the escape of fluid around the plunger I30.

In the operation of the modification shown in Figure 5, when the main plunger 46 and platen 41 are retracted by forcing oil into the auxiliary cylinders I6, the fluid displaced from the chambers I24 passes through the conduit H3 and port I28, into the cylinder bore I29, raising the plunger I30 and with it the counterweight I34. This action stores up potential energy which is available to effect the rapid advance of the platen 41 and main plunger 46, when fluid is released from the auxiliary cylinders I6 above the piston heads 52,

The modification shown in Figure 6 is similar to that shown in Figure 3, and merely discloses a commercial form of the press shown diagrammatically in Figure 3. The construction of this press is similar in general to the forms already described, except that a lining sleeve I40 is inserted in the, lower end of'the auxiliary cylinder I6 and the pneumatic piston heads 54 are of lesser diameter than the auxiliary piston heads 52, as in Figures 1 to 3, inclusive. In the arrangementof Figure 6, therefore. a much higher gas pressuremust be'used to raise themoving parts,

hend within our invention such modifications as come within the scope of the claims and the invention.

Having thus fully described our invention, what we claim as new and desire to secure by Letters Patent, is: 1

1. In combination, a main cylinder. having an upwardly acting main plunger therein, an auxiliary plunger connected to said main plunger and ofiset laterally therefrom for retracting said main plunger, pressure fluid supply means for alternately actuating said main and vsaid auxiliary plungers, an expansive fluid plunger directly connected to-said auxiliary plunger and in tandem arrangement therewith for rapidly advancing said main plunger, asource of expansive fluid under pressure constantly connected to said expansive fluid plunger and operating to force the said expansive fluid plunger in the same direction as said main plunger, the retracting operation of said auxiliary plunger operating through said expansive fluid plunger to compress said expansive fluid within said source. Y

2. In combination, a main cylinder having an upwardly acting main plunger therein, an auxiliary plunger connected to said main plunger and offset laterally therefrom for retracting said main plunger, pressure fluid supply means for alternately actuating said main and said auxiliary plungers, an expansive fluid plunger directly connected to said auxiliary plunger and in tandem arrangement therewith for rapidly advancing said main plunger, a source of expansive fluid under pressure constantly connected to said expansive fluid plunger and operating to force the said'expansive fluid plunger in the same direction as said main plunger, the retracting operation of said auxiliary plunger operating through said expansive fluid plunger to compress said expansive fluid within said source, said expansive fluid plunger having a larger head area than said auxiliary plunger.

WALTER ERNST.

LESLIE S. HUBBERT. 

